Page:Steamlocomotivec00ahrorich.djvu/86

 has been completed, the turret is turned through an angle to present another tool to the piston for the next operation, and the first tool remains in correct adjustment for use on the next piston in due course. The holes for the piston rod are bored with a large twist drill; and the next tool faces the piston on one side. A third tool turns the outside periphery, and a fourth operation cuts the two grooves in the periphery, into which the piston rings fit. These rings, two in number, are of cast iron, generally about ½ in. to ⅝ in. broad by ⅜ in. to ½ in. deep. The outside diameter of the ring is turned about ⅛ in. to ¼ in. larger